1. Field of the Invention
The present invention relates to turbo machines, and in particular relates to a turbo machine being able to prevent from instability in flow, by suppressing swirl due to recirculation flow at an inlet of an impeller and by suppressing rotation stalls of the impeller, irrespective of the types and the fluid thereof.
In more details, the present invention relates to the turbo machines, such as for a pump, a compressor, a blower, etc., having non-volume type impeller therewith, and in particular, relates to the turbo machine being able to prevent from the instability in flow, by suppressing a swirl or pre-whirl which is generated due to a main flow or component of the recirculation occurring at an inlet of an impeller and by suppressing rotation stalls thereof, thereby being suitable to be applied into a mixed-flow pump, which is used widely as water circulating pumps in a thermal power plant or in a nuclear power plant, a drainage pump, as well as, relates to a pump station into which is applied the turbo machine according to the present invention.
2. Description of Prior Art
Rotary machines being called by a name of xe2x80x9cturbo machinexe2x80x9d can be classified as below, depending upon the fluids by which the machines are operated and in types thereof.
1. With fluids by which the machine is operated:
Liquid, and Gas.
2. In Types:
An axial flow type, a mixed-flow type, and a centrifugal type.
In FIG. 24 showing a cross-section view of a mixed-flow pump which is now mainly or widely used due to easiness in operation thereof, it comprises a suction casing 11, a pump 12 and a diffuser 13, in a sequence from upper stream to down stream thereof.
A blade (of an impeller) 122 rotating within a casing 121 of the pump 12 is rotationally driven on a rotary shaft 123, thereby supplying energy to the liquid which is suctioned from the suction casing 11. The diffuser 13 has a function of converting a portion of velocity (or kinetic) energy of the liquid into static pressure.
FIG. 25 shows a typical characteristic curve between head and flow rate of the turbo machine including the mixed flow pump shown in FIG. 24, where the horizontal axis shows a parameter indicating the flow rate, while the vertical axis a parameter indicating the head.
Namely, the head falls down in reverse relation to increase of the flow rate in a region of low flow rate, however it rises up following the increase of the flow rate during the time when the flow rate lies within a S region (i.e., a portion uprising or jumping up at the right-hand side in the characteristic curve). And, when the flow rate rises up further, exceeding over the right-hand uprising portion of the characteristic curve, the head begins to fall down, again, following the increase in the flow rate.
Then, in a case where the turbo machine is operated with the flow rate of such the characteristic curve of uprising at the right-hand side, a mass of the liquid vibrates by itself, i.e., generating a surging phenomenon.
Such the characteristic curve of uprising at the right-hand side is caused, since the recirculation comes out at an outer edge of the inlet of the impeller when the flow rate flowing through the turbo machine is low, and at that instance, a flow passage or a channel for the liquid flowing into the turbo machine is narrowed, thereby generating a swirl in the liquid (see FIG. 24).
Since the surging gives damages not only upon the turbo machine, but also upon conduits or pipes which are connected to upper stream and down stream sides thereof, it is inhibited to be practiced in a region of low flow rate. Further, there were already proposed various methods for suppressing the surging as below, other than an improvement made in the shape (i.e., profile) of the blade, for the purpose of expanding or enlarging the operation region of the turbo machine.
1. Casing Treatment
Thin or narrow grooves or drains, being from 10% to 20% of a chordal length of the blade, are formed in a casing region where the impeller lies, so as to improve a stall margin.
FIGS. 26(a) and (b) show explanatory views of the casing treatment which were already proposed, in particular, FIG. 26(a) shows a positional relationship between the casing treatment and the blades, and FIG. 26(b) shows the cross section views of the casing treatment.
Namely, with the casing treatment which were already proposed, the grooves being sufficient in the depth are formed in an inner wall (i.e., flow surface) of the casing on the region where the blades lie, in an axial direction, in a peripheral direction, or in an oblique direction, alternatively, in a radial direction or an oblique direction, respectively.
Though is not yet investigated clearly the mechanism on how the casing treatment enables the improvement in the stall margin theoretically, it can be considered that because the fluid of high pressure is spouted out or injected into a low energy region and inhibits occurrence of the installing cells.
2. Separator
A separator is provided for dividing the recirculation flow occurring at the outer edge of the inlet of the impeller into a reverse flow portion and a forward flow portion (i.e., in a main flow direction), in the region of low flow rate, thereby prohibiting the expansion of the recirculation.
FIGS. 27(a)-(c) are explanatory views for the separators, each of which is applied to the turbo machine of the axial flow type, in particular, there are proposed a suction ring type (in FIG. 27(a)), a blade separator type (in FIG. 27(b)), and an air separator type (in FIG. 27(c)), respectively.
In the suction ring type (in FIG. 27(a)), the reverse flow is enclosed within an outside of the suction ring, and in the blade separator type (in FIG. 27(b)) is provided a fin between the casing and the ring. Further, with the air separator type (in FIG. 27(c)), a front end or a tip of the moving wing (i.e., the blade) is opened so as to introduce the reverse flows into the outside of the casing, thereby prohibiting the swirl from being generated due to the reverse flows by means of the fin. Thus, it is more effective, comparing with the former two types mentioned, however, comes to be large-scaled in the devices thereof.
3. Active Control
This is to suppress the generation of the swirl due to the recirculation by injecting or spouting out the high pressure fluid from an outside into a spot where the recirculation occurs.
Furthermore, as an example of the conventional turbo machines, a mixed-flow pump will be described hereinafter. To a mixed-flow pump, it is required to show a head-flow rate characteristic curve (hereinafter, called by xe2x80x9chead curvexe2x80x9d) having no behavior uprising at the right-hand side for enabling a stable operation, in a case where the pump is operated over the whole flow range thereof. However, ordinarily in a pump, it is common that the characteristics, such as an efficiency representing performance of the pump, a stability of the head curve, a cavitation performance, and an axial motive power for closure, etc., are in reversed relationships to one another. Namely, if trying to improve one of those characteristics, the other one(s) is is decreased down, therefore there is a problem that it is difficult to obtain improvements in at least two or more characteristics at the same time. For example, with a pump in which consideration was made primarily onto the efficiency thereof, the head curve shows a remarkable behavior uprising at the right-hand side in a portion thereof, thereby it has a tendency to be unstable.
For obtaining a head curve continuously falling down at the right-hand side for enabling the stable operation, in the conventional arts, as is mentioned in the above, it is already known that the casing treatment or the separator is provided or treated therein. Such the structure is already described, for example in U.S. Pat. No. 4,212,585.
However, in accordance with the casing treatment and the separators of the prior arts mentioned above, although it is possible to shift the characteristic curve between head and flow rate including the portion uprising at the right-hand side into the lower flow rate side as it is, so as to expand the stable operation region thereof, however it is impossible to remove or cancel such the characteristic or behavior uprising at the right-hand side. Further, the turbo machine is decreased down by approximately 1% in the efficiency thereof, if it rises up by an every 10% in the stall margin, in accordance with the casing treatment.
Also, it is not easy work to machine deep grooves in an inner wall of the casing in the axial direction thereof. Moreover, there is a problem that such the casing treatment cannot be applied to a closed-type impeller having such as a shroud thereabouts.
Further, in such the active control, since there is a necessity to obtain the high pressure fluid from the turbo machine itself or an outside thereof, it is impossible to escape from the decrease in the efficiency of the turbo machine system as a whole.
An object in accordance with the present invention is, for dissolving the drawbacks in the conventional art mentioned in the above, to provide a turbo machine, with which not only removing such the behavior uprising at the right-hand side from the characteristic curve between the head and the flow rate, but also being able to suppress the decrease in the efficiency, i.e., suppressing the swirl generated due to the recirculation occurring at the inlet of the impeller and the rotating stall of thereof.
Namely, an object according to the present invention is to provide a turbo machine which has the head-flow rate characteristic curve without such the behavior of failing down at the right-hand side, as well as can also obtain high efficiency therewith.
Further, another object according to the present invention is to provide a turbo machine, with which can be obtain such the head-flow rate characteristic curve without the behavior of falling down at the right-hand side, as well as can be manufactured with ease.
Furthermore, other object according to the present invention is to provide a turbo machine having the closed-type impeller, with which also can be obtain such the head-flow rate characteristic curve without such the behavior of falling down at the right-hand side.
According to the present invention, for accomplishing the above-mentioned object, there is provided a turbo machine comprising:
a casing having a flow surface defined therein;
an impeller having a plurality of blades and being positioned within said casing;
a plurality of grooves being formed in the flow surface of said casing, for connecting between an inlet side of said impeller and an area in which the blades of said impeller reside, wherein each of said grooves has a length at least part of which is oriented in an axial direction of the casing, a width measured in a circumferential direction, and a depth, and wherein the width of each of said grooves is equal to or greater than the depth thereof.
Also, according to the present invention, for accomplishing the above-mentioned object, there is provided a turbo machine comprising:
a casing having a flow surface defined therein;
an impeller having a plurality of blades and being positioned within said casing;
a plurality of grooves being formed in the flow surface of said casing, for connecting between an inlet side of said impeller and an area in which the blades of said impeller reside, wherein each of said grooves is at least equal to 5 mm or greater than that in a width.
Also, according to the present invention, there is provided a turbo machine comprising:
a casing having a flow surface defined therein;
an impeller having a plurality of blades and being positioned within said casing;
a plurality of grooves being formed in the flow surface of said casing in radial direction thereof, for connecting between an inlet side of said impeller and an area in which the blades of said impeller reside in a gradient direction of fluid pressure therein, wherein each of said grooves is at least equal to 5 mm or greater than that in a width, and
a terminal position at downstream side of each of said grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of swirl at a terminal position of each of said grooves at upstream side thereof.
Further, according to the present invention, there is provided a turbo machine comprising:
a casing having a flow surface defined therein;
an impeller having a plurality of blades and being positioned within said casing;
a large number of shallow grooves being formed in the flow surface of said casing, for connecting between a spot where swirl is generated in a low flow rate of fluid at an inlet side of said impeller and an area in which the blades of said impeller reside in a direction of pressure gradient of the fluid, wherein each of said grooves is at least equal to 5 mm or greater than that in width thereof, and
a terminal position at downstream side of each said groove is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of the swirl at a terminal position at upstream side of each said groove, thereby removing a behavior of uprising at the right-hand side from a head-flow rate characteristic curve of said turbo machine.
Furthermore, according to the present invention, in the turbo machine as defined in the above, wherein said grooves are preferably formed approximately from 30% to 50% in the width thereof, at a ratio with respect to a total circumference length of the casing where the grooves are formed, and are formed approximately from 0.5% to 1.6% in the depth thereof, in more details from 2 mm to 4 mm.
According to the present invention, for accomplishing the above-mentioned object, there is also provided a turbo machine comprising:
an open-type impeller having a plurality of blades therewith;
a casing having a flow surface defined therein and being positioned with said impeller therein;
a plurality of grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein:
a bottom surface of each of said grooves is so constructed that it is equal or higher than the flow surface of said casing being adjacent thereto in height thereof.
Further, according to the present invention, there is also provided a turbo machine comprising:
an open-type impeller having a plurality of blades therewith;
a casing having a flow surface defined therein and being positioned with said impeller therein;
a plurality of grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein:
the flow surface of said casing being adjacent with a lower flow at a terminal end of each of said grooves is formed so that it is at same level of the bottom surface of each said groove or lies in a direction of an external diameter thereof, the outer periphery to portion of said impeller at the inlet side of the blades thereof opposing to a groove portion is so constructed that it is low in height of the blade thereof corresponding to the groove portion, while the height of the each blade of said impeller in a lower flow side than said grooves is higher than that at the portion opposing to that of said groove portion.
In addition thereto, according to the present invention, there is also provide a turbo machine comprising:
an open-type impeller having a plurality of blades therewith;
a casing having a flow sur face defined therein and being positioned with said impeller therein;
a large number of shallow grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof and being equal or greater than 5 mm in depth thereof, for connecting between a spot where swirl is generated in a low flow rate of fluid at an inlet side of said impeller and an area on the interior surface of said casing in which the blades of said impeller reside in a direction of pressure gradient of the fluid, on a periphery thereof, wherein:
a terminal position at downstream side of each of said grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of the swirl in inlet main flow at a terminal position of each of said grooves at upstream side thereof, thereby removing a behavior uprising at the right-hand side from a head-flow rate characteristic curve of said turbo machine, and
a bottom surface of each said grooves is so constructed that it is equal or higher than the flow surface of said casing being adjacent thereto in a height thereof, as well as the outer periphery portion of said impeller at the inlet side of the blades thereof, opposing to a groove portion, is so constructed that it is low in height at the blades thereof corresponding to that groove portion.
Further, according to the present invention, there is provided a turbo machine comprising:
an open-type impeller having a plurality of blades therewith;
a casing having a conical wall surface therein and being positioned with said impeller therein;
a plurality of grooves being formed in a direction of pressure gradation so as to project from the conical wall surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, wherein:
height of each of the blades on a meridian plane in vicinity of an inlet of said impeller is made to be smaller than that on a meridian plane in vicinity of an outlet of said impeller, and those heights of the blades are determined corresponding to height of a groove portion.
Further, according to the present invention, there is provided a turbo machine comprising:
an open-type impeller having a plurality of blades therewith;
a casing having a flow surface defined therein and being positioned with said impeller therein;
a plurality of grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein:
a configuration of flow passage defined with projecting portions of said grooves is so constructed that it is larger than that which is defined in the casing at downstream side of said grooves and is elongated into upstream side as it is, in a distance of a radical direction from a rotation center of a pump;
a tip portion of said impeller is so formed that it defines an approximate constant space between said grooves and the interior surfaces of said casing; and
height of each the blades of said impeller in vicinity of a terminal end of said grooves is made higher than that of the blade at downstream side.
Further, according to the present invention, there is also provided a turbo machine comprising:
a closed-type impeller having a plurality of blades and a shroud thereabouts;
a casing having a inner wall and being positioned with said impeller therein, wherein said impeller is formed into an open-type having no shroud thereabouts in vicinity of an inlet of said impeller; and
a plurality of grooves in a direction of pressure gradient, being formed on the inner wall of said casing opposing to that portion in vicinity of the inlet of said impeller having no shroud thereabouts, on a periphery thereof, wherein:
a starting end of each of said grooves at an inlet side is positioned at a side being upper in flow than a tip inlet side of said impeller, while a terminating end of said each groove is positioned at a lower flow side than a tip outlet side of said impeller.
Further, according to the present invention, there is also provided a turbo machine comprising:
a closed-type impeller having a plurality of blades and a shroud thereabouts;
a casing having a flow surface defined therein and being positioned with said impeller therein, wherein said impeller is formed into an open-type having no shroud thereabouts in vicinity of an inlet of said impeller; and
a large number of shallow grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof and being equal or greater than 5 mm in depth thereof, for connecting between a spot where swirl is generated in a low flow rate of fluid at an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside in a direction of pressure gradient of the fluid, on a periphery thereof, wherein:
a terminal position at downstream side of each of said grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of the swirl in inlet main flow at a terminal position, at upstream side of each of said grooves, thereby removing a behavior of uprising at the right-hand side from a head-flow rate characteristic curve of said turbo machine; and
a bottom surface of each of said grooves is so constructed that it is equal or higher than the flow surface of said casing adjacent thereto in height thereof, as well as the outer peripheral portion of said impeller at the inlet side of the blades thereof opposing to a groove portion is so constructed that it is low in height of the blades of said impeller corresponding to that groove portion.
Further, according to the present invention, there is provided a turbo machine as defined in the above, further comprising an axis sealing portion for sealing between a minimum radial portion of the shroud of said impeller and said casing, wherein said axis sealing portion includes a mouth ring portion and a casing ring portion.
Also, according to the present invention, there is also provided a turbo machine comprising:
an impeller having a plurality of blades therewith;
a casing having a flow surface defined therein and being positioned with said impeller therein; and
a plurality of grooves being formed on the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein:
a terminal position at downstream side of each of said grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of the swirl in inlet main flow at a terminal position, at upstream side of each of said grooves, thereby removing a behavior of uprising at the right-hand side from a head-flow rate characteristic curve of said turbo machine; and
a portion of said casing where said grooves are provided is constructed separate from other portion of said casing.
Further, according to the present invention, in the turbo machine as defined in the above, wherein a portion of said casing, on which said grooves are formed, is separately constructed and assembled from other portion of said casing being divided in a radical direction thereof.
Furthermore, according to the present invention, in the turbo machine as defined in the above, wherein said grooves are formed in a direction being inclined from a direction of pump axis to a rotating direction of said impeller, at starting ends thereof.
And, according to the present invention, for accomplishing the above object, there is also provide a turbo machine comprising:
an impeller having a plurality of blades therewith;
a casing having a flow surface defined therein and being positioned with said impeller therein; and
a plurality of grooves being formed in the flow surface of said casing, for connecting between an inlet side of said impeller and an area on the interior surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein an index of determining a form of said grooves is obtained by a following equation:
JE No.=WRxc3x97VRxc3x97WDRxc3x97DLDR
xe2x80x83where,
WR (a width ratio) is a value obtained by dividing a total value of the groove widths W with a length of casing periphery;
VR (a volume ratio) is a value obtained by dividing a total volume of said grooves with a volume of said impeller;
WDR (a width-depth ratio) is a value obtained by dividing the width W of said groove with a depth D of said groove; and
DLDR is a ratio between a length of said groove in flow, being lower than the impeller inlet and the depth of said groove, and wherein, said grooves are formed so that the index JE No. lies in a range from 0.03 to 0.5.
Further, according to the present invention, in the turbo machine as defined in the above, wherein said grooves are formed so that the index JE No. lies in a range from 0.15 to 0.2.
Moreover, according to the present invention, for accomplishing another object mentioned above, there is provided a pump station for lifting up a fluid head in a suction side up to a discharge side, comprising:
a pump having an impeller and a casing being positioned with said impeller therein, for pumping up the fluid in the suction side;
a passage for conducting the fluid being pumped up from said pump to the discharge side;
a driver apparatus for ratably driving said impeller of said pump; and
controller means for controlling rotation speed of said impeller of said pump, wherein said pump is the pump defined in the above.
Further, according to the present invention, in the pump station as defined in the above, wherein a specific speed Ns is approximately from 1,000 to 1,500 assuming that rotation speed of said pump used in said pump station is N (rpm), a total head H (m), and a discharge flow rate Q (m3/min), and that the specific speed Ns as an index of indicating a pump characteristic is obtained by an equation, Ns=Nxc3x97Q0.5/H0.75, and when a stationary head being determined by a suction side fluid level and a discharge side fluid level is equal or greater than 50% of a head at a specific point.
Further, according to the present invention, in the pump station as defined in the above, wherein a rotation speed of said driver apparatus is controlled in a control range from 60% to 100% with respect to a reference rotation speed, in a case where said driving apparatus for the pump comprises a speed reduction gear, a fluid coupling and a diesel engine.
Further, according to the present invention, in the pump station as defined in the above, wherein a rotation speed of said driver apparatus is controlled in a control range from 60% to 100% with respect to a reference rotation speed, in a case where said driving apparatus for the pump comprises a speed reduction gear, a fluid coupling and a gas turbine.
And, according to the present invention, in the pump station as defined in the above, wherein a rotation speed of said driver apparatus is controlled in a control range from 0% to 100% with respect to a reference rotation speed, in a case where said driving apparatus for the pump comprises an electric motor for controlling the rotation speed by an inverter.
Also, according to the present invention, there is provided a turbo machine comprising:
an impeller having a plurality of blades therewith;
a casing having a flow surface defined therein and being positioned with said impeller therein; and
a plurality of grooves being formed on the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein:
each of said grooves has a length at least a part of which is oriented in an axial direction of the casing and a width measured in a circumferential direction of the casing of at leas 5 mm, and wherein a terminal position at downstream side of each of said grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of the swirl in inlet main flow at a terminal position, at upstream side of each of said grooves, thereby removing a behavior of uprising at the right-hand side from a head-flow rate characteristic curve of said turbo machine; and
wherein said grooves are defined by a plurality of spaced ribs having a length at least part of which is oriented in the axial direction of the casing, the ribs being constructed separately from the casing and being fixed therein.
Further, according to the present invention, there is provided a method for manufacturing a turbo machine, comprising:
providing a casing having a flow surface defined therein and a channel provided in the flow surface;
providing a plurality of ribs in the channel, each of the ribs being arranged in the channel so as to have a length at least a part of which is oriented in an axial direction of the casing, the ribs being spaced from one another to define a plurality of grooves therebetween, each of the grooves having a length at least a part of which is oriented in the axial direction of the casing and a width measured in a circumferential direction of the casing;
fixing the ribs in the channel; and
positioning an impeller having a plurality of blades within the casing such that the plurality of grooves oppose an outer peripheral portion of said impeller at an inlet side thereof, for connecting between an inlet side of said impeller and an area on the flow surface of the casing in which the blades of the impeller reside, on a periphery thereof, wherein
a terminal position at a downstream side of each of the grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of swirl in inlet main flow at a terminal position at an upstream side of each of the grooves, thereby removing a behavior of uprising at the right-hand side from a head-flow rate characteristic curve of the turbo machine.